The invention relates to dairy equipment, and more particularly to milking clusters.
A milking cluster is an assembly attached to the dairy animal's udder during milking. The cluster includes a claw, four shell assemblies, four short milk tubes, four air tubes, and an air fork. Each shell assembly includes an outer shell and an inner liner called an inflation. The short milk tube connects the inflation to the claw which in turn is connected to a milk transport hose subject to vacuum or negative pressure. The air tube connects the space between the inflation and the shell to the air fork. The air fork is connected through one or more air lines to a pulsation device cycling vacuum off and on.
When milking a dairy animal, the inside bore of the inflation is at the system vacuum level, and the space between the inflation and the shell is either at vacuum or at atmospheric pressure depending on the cycle of the pulsation device. When there is atmospheric pressure on the outside of the inflation in the space between the inflation and the shell, the vacuum on the inside of the inflation causes the inflation to collapse. This is known as the rest phase, during which there is no milk flow, i.e. liner closed. When there is vacuum on the outside of the inflation in the space between the inflation and the shell, such vacuum balances the vacuum on the inside of the inflation, and the inflation can relax or expand. This is the milk phase, during which milk flows, i.e. liner open. Most milking clusters operate efficiently with pulsation rates between 45 and 60 cycles per minute. The pulsing movement massages the teat. In the rest phase, the collapse of the inflation squeezes the teat, forcing blood in the teat to circulate. Without this rest phase, blood would not circulate throughout the teat, and injury to the teat might result. The milk phase and the rest phase may have some overlap.
The purpose of the air fork is to distribute the vacuum and atmospheric air pulses to the shells, to apply the cycling vacuum and atmospheric air pulses to the space between the inflation and the shell. Pulsation systems are either simultaneous (sometimes called single shot) or alternating. Simultaneous means that all four teat cups will be in either the milk phase or the rest phase at the same time. Alternating pulsation systems will have the two front teat cups in the milk phase and the two rear teat cups in the rest phase at one time, and then alternate to just the opposite. Alternating pulsators are usually more desirable because they provide more even milk flow, excellent vacuum stability, and the option of adjusting the two rear teat cups to a greater milk/rest ratio than the two front teat cups.
It is desirable that the teat cup remain attached to the teat until milking is completed, otherwise there is a rapid admission of air into the now open upper mouth of the liner, which is undesirable. One cause of such detachment is movement of the dairy animal if she lifts one or her rear legs and steps forward because the dew claw on the inside of her leg just above the hoof can hook the air tube between the air fork and the respective teat cup, and pull the teat cup off the teat. The present invention addresses and solves this problem.